Cooling and noise reducing arrangement for stationary induction apparatus



3,305,813 AND NOISE REDUCING ARRANGEMENT FOR STATIONARY INDUCTION APPARATUS 2 Sheets-Sheet 1 1, 1967 L. R. TOOTHMAN ETAL COOLING Filed Nov. 21, 1961 L S. L S INVENTORS,

- Lawrence R 750172227477 am) flttorm'y 9 L. R. TOOTHMAN ETAL COOLING AND NOISE REDUCING ARRANGEMENT FOR STATIONARY INDUCTION APPARATUS 2 Sheets-Sheet 2 Filed NOV. 21, 1961 Leo S [.06 9am IN V EN TORS-A Umrd w, Paw 915 3,305,813 V COOLING AND NOISE REDUCING AR- RANGEMENT FOR "STATIQNARY IN-' DUCTEON APPARATUS j. Lawrence R. Toothrnan, Houston, and Leo S. La Sota,

Carnegie, Pa., assignors to McGraw-Edison Milwaukee, Wis., a corporation of Delaware Filed Nov. 21, 1961, Ser. No. 154,006 9 Claims. (Cl. 336-100) This invention relates to, stationary induction appa- 1 ratus andv in particular to an arrangement forcooling and reducing audible noise generated by stationary induction apparatus. y

This invention is an improvement over the apparatus Company, I

disclosed in the copending application of Charles C.

Honey, Kenneth C. Stewart, and Lawrence R. Toothman, Serial No. 781,163 filed December 17, 1958, now Patent No. 3,102,246, entitled Noise Reducing Means for Transformer. In the encased, oil-immersed, stationary inducnetic core due to magnetostriction and coupled to casing walls through the dielectric liquid are reduced by compliant elements which change the compressibility of the .tion apparatus of the Honey et al. application, the sound wave energy and vibratory forces originating in the magdielectric liquid. The compliant elements preferably comprise elongated, thin-walled, compressible tubes filled with gas and immersed in the dielectric liquid between the transformer core and coil assembly and the walls of the casing. The gas filled tubes have compliant walls and change in volume at a frequency dependent upon the vipressible dielectric liquid between core and coil and the tank walls by changes in volume which increase the compressibility of the liquid and reduce the sound emitted from the tank Walls. The compliant tubes are spaced apart peripherally of the tank walls so that they do not interfere with direct circulation of dielectric liquid between the core and coil assembly and the tank walls.

It is an object of the invention to provide stationary induction apparatus having the noise reducing compliant tube means of the Honey et al. application and improved means for cooling the apparatus.

It is a further object of the invention to provide oilimmersed stationary induction apparatus having means which absorbs both heat and vibratory forces from the oil to cool the apparatus and reduce the audible noise emanating therefrom.

The objects and advantages of the invention will be better understood from the following detailed description when taken in conjunction with the accompanying drawing wherein:

FIG. 1 is a vertical sectional view through an electrical transformer embodying the invention;

FIG. 2 is a partial vertical sectional view through an alternative embodiment which uses different gaseous mediums for the cooling means and the gas cushion above the transformer oil; and

FIG. 3 is a plan view of encased stationary induction apparatus embodying the invention wherein the temperature is more nearly equal throughout the casing than in the embodiments of FIGS. 1 and 2, the cover being removed to better illustrate the elements.

Referring to FIG. 1 of the drawing, a metallic tank 10 3,305,813 v Pat'entedfeb. 21, 1 337 2 having a bottom wall 11, pairs of opposed vertical sidewalls 12, and a cover 14 is filled with a suitable insulating dielectric liquid 15 such as transformer oil to a level 16. A cushion of gaseous insulating dielectric 17 having high thermal conductivity such as octafluoropropane, C 1 is provided withintank 10 above the oil 15. A transformer core and coil assembly 19 immersed in the oil 15 within tank 10 includesa magnetic core 20 comprising a plurality of leg laminations 22 and yoke laminations 23 of. magnetic steel. The assembled leg laminations 22 form vertical winding legs surrounded by cylindrical coils-25 and connected at their upper and lowe-rends by upper and lower yokes formed by the yoke laminations 23. Channel iron side frame members 27 are disposedon opposite sides of and bolted to the upper and lower core yokes. Energization of the electrical windings 25 surrounding the core winding legs results in alternating magnetization of the'core 20. The magnetic steel laminations 22 and 23 cyclically expand and contract due'to the phenomenon of magnetostriction when magnetized and demagnetized by the current flowing in the windings 25. The magnetic core 20 thus acts as a source of cycle vibrations and harmonics thereof.

.Means provided for resiliently supporting the core and *coilassembly 19 and affording maximum mechanical decoupling between the vibration propagatingdeviceZO and the transformer casing 10 includes helical springs 28 disposed within tubular housings 30, supported from the tank bottom wall 11. Transverse support members 32 positioned .below and, fitting within cutout portions (not shown) in the lower'side frame members 27 rest upon the springs 28 which extend above the upper end of the tubular housings 30 and resiliently support the core and coil .assembly 19 so that it is outof direct contact with the tank 10. Such resilient supporting means for the core and coil assembly is disclosed in the copending application of Morton Aronson and John F. Koepke, Serial No. 130,920, now Patent No. 3,125,736, entitled Stationary Induction Apparatus Having Means for Reducing Audible Noise, filed August 11, 1961, and having the same assignee as this application and to which reference is made for details of construction.

The transformer oil 15 also transmits the vibratory forces and sound pressure waves originating in the magnetic core 20. Since the oil 15 itself is nearly incompressible, the oil 15 strongly couples the vibrations of core 20 to the tank bottom 11 and sidewalls 12 which are forced into vibration as panels and radiate audible sound. Further, sound pressure waves'set up in the oil 15 are transmitted by the oil to the walls of tank 10 and throng the walls of tank 10 to the surrounding air. 1

In accordancewith the aforementioned Honey et al. application, both the vibratory forces and the sound pressure waves transmitted by the oil 15 from the core 20 to the tank walls are shuntedby elongated compliant tubes 34 and 38 interposed in the-oil 15 between the core 20 and the tank walls which increase the effective compressibility, or reduce the stiffness of the oil 15. As illustrated, the compliant elements 34 are thin-walled tubes of U-shape having vertical leg portions 35 positioned adjacent one pair of opposed tank sidewalls 12 and a horizontal cross-piece 36 positioned adjacent the bottom wall 11 of the tank 10. Preferably, the tubes 34 are mounted away from the tank sidewalls 12 and bottom .wall 11 in spaced apart relation peripherally of said one r of the vibratory source.

in sealed relation thereto.

elongated, thin-walled compliant tubes 38 having closed lower ends may be affixed in spaced apart parallel relation contiguous the other pair of opposed tank sidewalls 12 by mounting blocks 37 so that the open end of the tubes 38 is above the surface 16 of the oil 15 and in communication with the gas cushion 17.

The compliant tubes 34 and 38 are thus dis-posed in spaced apart parallel relationship in plane arrays in the path of the incident vibratory forces originating in the magnetic core 20 and transmitted by the dielectric liquid 15. The compliant tubes 34 and 38 change in volume and effectively increase the compressibility of the oil 15 in amanner analogous to that in which a mixture of air bubbles and a liquid lowers the velocity of sound in the liquid. The volume of the tubes 34 and 38 changes at a frequency dependent upon the source of vibration, and the tubes 34 and 38 go into resonance at the frequency The Honey et al. application discloses by the method of dynamic analogies that the elemental oil mass goes into resonance with the stiffness and elemental mass of the compliant tubes in a shunting network which reduces the vibratory force on the enclosure wall. Preferably, the stiffness constant of the compressible tubes 34 and 38 is selected so that the mechanical stiffness reactance and the mechanical inertial reactance due to the mass of the oil and the mass of the compliant elements are in series resonance at the frequency of the force generator so that the compliant tubes are tuned for resonance. Since high compliance is one factor in obtaining reduced transformer noise levels, materials are selected for the tubes 34 and 38 which have a low modulus of elasticity and high tensile strength. This combination of properties provides a high static deflection characteristic and assures that the stress limit of the material is not exceeded. The tubes 34 and 38 are also selected to have high thermal conductivity, and thinwalled,round metallic tubes of material such as aluminum deformed to elliptical cross section are satisfactory to accomplish the improved results of the invention. An odd number of compliant resonant tubes in an array results in greater absorption of sound energy, and effective reduction of radiated sound is obtained with spaced apart arrays each of which comprises an odd number of compliant tubes.

For promoting circulation of the gaseous medium 17 through the tubes in heat exchange relation with the transformer oil 15 and dissipating the heat absorbed by the gaseous medium in passing through the tubes, conduit means are provided communicating with the inlet and outlet ends of the tubes. Such conduit means may connect with the tubes 34 and 38 individually or with different portions of the gas cushion 17, but in the preferred embodiment shown in FIG. 1 one open end of all the U-shaped compressible tubes 34 registers with an intake manifold 39 disposed adjacent one of the pair of opposed tank sidewalls 12 and the other open end of all the U-shaped tubes 34 registers with an exhaust manifold 40 disposed adjacent the opposite tank sidewall 12. The conduit means may include an intake header 41 communicating with the intake manifold 39 and extending through a wall of tank in sealed relation thereto and an' exhaust header 42 communicating with the exhaust manifold 40 and extending through a wall of tank 10 The conduit means may also include a conduit 44 external of tank 10 connecting the headers 41 and 42. Air cooling of the conduit 44 external of the tank will ordinarily be sufficient for dissipating the heat absorbed by the gas 17 from the liquid dielectric in passing through the tubes 34, but, if desired, a heat exchanger 47 may be included in conduit 44 and is illustrated as comprising cooling fins 48 and a fan 49 for continuously circulating air past the fins 48.

Conduit 44 may include a fan 54 for promoting circulation of the gaseous insulation 17 through the compliant tubes 34 by suction. A constriction 55 may he provided on the pressure side of the blower 54 to assure that the gaseous dielectric medium 17 does not enter the tubes 34 at a pressure greater than that within the tank 10. The gaseous insulating dielectric medium 17 has high thermal conductivity and is in heat exchange relationship with the transformer oil 15 in passing through the tubes 34 which are of high thermal conductivity. The gaseous medium 17 thus absorbs heat-from the transformer oil 15 and dissipates it in the heat exchanger 47 to cool the core and coil assembly 19 while the tubes 34 are resonating and absorbing the vibratory forces and sound pressure waves transmitted by the transformer oil.

In the embodiment of FIG. 1 the open ends of the compliant tubes 34 communicate with the gas cushion above the oil, and the gaseous medium 17 forming such cushion circulates through the compliant tubes 34 and the conduit means including manifolds 39 and 40, headers 41 and 42, and heat exchanger 47. vIn the embodiment of FIG. 2 the compliant tubes 34 and the conduit means communicating with the tubes 34 constitute a closed cooling system sealed from the gas cushion and in which a different gas may circulate. The intake end of each compliant tube 34 is joined in sealing relation to the intake manifold 39 and the outlet end of each tube 34 registers with and is sealed to the exhaust manifold 40.

The gas 61) circulating through the compressible tubes 34, the manifolds 39 and 40', the headers 41 and 42, the blower 54 and the heat exchanger 47 may be a gas such as octafiuoropropane, C 1 having high thermal conductivity whereas the gas cushion 17 may comprise a noncondensable gas such as nitrogen.

The embodiment of FIG. 3 assures greater equality of temperature throughout the transformer tank 10 than the embodiments of FIGS. 1 and 2. The compressible U-shapedtubes 34 are divided into two groups A and B each of which is disposed in one half of the tank 10 and has intake and exhaust manifolds 39 and 40 associated -therewith respectively in communication with the intake and exhaust ends of the compliant tubes 34 of said group. Conduit means 61 connect the intake manifold 39A of group A with the exhaust manifold 40B of group B and conduit means 62 connect intake manifold 39B of group B with the exhaust manifold 40A of group A so that the gaseous medium 17 first circulates through the tubes 34 of group A in one half of the tank 10 and is then passed to the tubes 34 of group B in the other half of the tank. Each conduit means 61 and 62 is illustrated as including a blower 54, a heat exchanger 47, and a constriction 55 on the pressure side of the blower 54.

Although the invention has been illustrated and described with the gaseous medium circulating only through the U-shaped compressible tubes 34, it will be appreciated that the invention is not so limited and that cooling of the transformer can also be effected by circulating the gaseous medium through the straight compliant tubes 38 lining the other pair of opposed tank sidewalls 12 while said tubes 38 resonate and absorb the vibratory forces and sound pressure waves transmitted by the coil.

While only a few embodiments of the invention have been illustrated and described, many modifications and variations thereof will be apparent to those skilled in the art, and consequently it is intended to cover in the appended claims all such modifications and variations which fall within the true spirit and scope of the invention.

What we claim is new and desire to secure by Letters Patent of the United States is:

1. In combination, a tank, an insulating dielectric liquid partially filling said tank, a gaseous dielectric medium filling said tank above said liquid dielectric, a transformer core and coil assembly immersed in said liquid dielectric within said tank and including a magnetic core and electrical windings linking said core, means for reducing the 5 vibratory forces originating in said magnetic core transmitted by said dielectric liquid tending to vibrate the Walls of said tank including a plurality of elongated, hollow, thin-Walled spaced apart, U-shaped, compliant tubes of high thermal conductivity immersed in said dielectric liquid adjacent the bottom wall and sidewalls of said tank and having open ends in communication with said gaseous medium, intake and exhaust manifolds each of which registers with one open end of said tubes, means including conduit means communicating with said manifolds for inducing circulation of said gaseous medium through said tubes, and means in said conduit means for cooling said gaseous medium after it has circulated through said tubes.

2. In combination, a tank, an insulating liquid within said tank, a transformer core and coil assembly immersed in said liquid within said tank including a magnetic core and electrical windings linking said core, means for reducing the vibratory forces originating in said magnetic core transmitted by said liquid tending to vibrate the walls of said tank including a plurality of elongated, hollow, thin-Walled, U-shaped compliant tubes of relatively high thermal conductivity immersed in said dielectric liquid between said core and coil assembly and the bottom and side walls of said tank, a gaseous medium filling said tubes, intake and exhaust manifolds each of which is in communication with one end of said U- shaped tubes, means including conduit means communicating with said manifolds for inducing circulation of said gaseous medium in a path through said tubes and from said exhaust manifold through said conduit means back to said intake manifold, and means in said conduit means for cooling said gaseous medium after it has circulated through said tubes and absorbed heat from said insulating liquid.

3. In combination, a tank, insulating liquid dielectric within said tank, a transformer core and coil assembly immersed in said liquid dielectric within said tank including a magnetic core and electrical windings linking said core, means for reducing the vibratory forces originating in said core transmitted by said liquid dielectric tending to vibrate the walls of said tank including a plurality of elongated, thin-walled, U-shaped, spaced apart, compliant tubes of relatively high thermal conductivity immersed in said liquid dielectric between said core and coil assembly and the bottom and side walls of said tank, a gaseous medium filling said tubes, means including conduit means communicating with the ends of said U-shaped tubes for inducing the circulation of said gaseous medium through said tubes in heat exchange relationship with said liquid dielectric, and means for dissipating the heat absorbed by said gaseous medium from said liquid dielectric in circulating through said tubes.

4. In combination, a tank, liquid dielectric within said tank, a transformer core and coil assembly immersed in said dielectric Within said tank including a magnetic core and electrical windings linking said core, means for mechanically decoupling said core and coil assembly from the walls of said tank, means for reducing the vibratory forces originating in said core transmitted by said liquid dielectric tending to vibrate the walls of said tank including a plurality of elongated, thin-Walled, spaced apart, compliant tubes of relatively high thermal conductivity immersed in said liquid dielectric between said core and coil assembly and the walls of said tank, a gaseous medium having relatively high thermal conductivity filling said tubes, intake and exhaust manifolds each of which is in communication with one end of said tubes, means including conduit means communicating with said manifolds and extending through the walls of said tank for promoting circulation of said gaseous medium in a path through said tubes, wherein said gaseous medium is in heat exchange relationship with said liquid dielectric, and from said exhaust manifold through said conduit means back to said intake manifold, and means in said conduit 6 means for dissipating the heat absorbed by said gaseous medium from said liquid dielectric in circulating through said tubes.

5. In combination, a tank, an insulating liquid dielectric within said tank, a transformer core and coil assembly immersed in said liquid dielectric within said tank including a magnetic core and electrical windings linking said core, means for reducing the vibratory forces originating in said core transmitted by said liquid dielectric tending to vibrate the walls of said tank including a plurality of elongated, thin-walled, spaced apart, compressible tubes of relatively high thermal conductivity immersed in said dielectric liquid between said core and coil assembly and the walls of said tank, a gaseous medium filling said tubes, means including conduit means communicating with the ends of said tubes for inducing circulation of such gaseous medium in a path through said tubes and said conduit means, said last-named means also including means for dissipating the heat absorbed by said gaseous medium from said liquid dielectric in circulating through said tubes.

6. In combination, a tank, insulating liquid dielectric within said tank, a transformer core and coil assembly immersed in said dielectric within said tank including a magnetic core and electrical windings linking said core, means for mechanically decoupling said core and coil assembly from the walls of said tank, means for reducing the vibratory forces originating in said core transmitted by said liquid dielectric tending to vibrate the walls of said tank including a plurality of elongated, thin-walled, spaced apart, compliant tubes of relatively high thermal conductivity immersed in said liquid dielectric between said core and coil assembly and the walls of said tank, a gaseous medium having relatively high thermal conductivity filling said tubes, intake and exhaust manifolds each of which is in communication with one end of said tubes, conduit means extending through the wall-s of said tank and communicating with said manifolds, means including a blower in said conduit means for inducing circulation of said gaseous medium in a path through said tubes, said exhaust manifold, said conduit means, and said intake manifold back to said tubes, and a heat exchanger in said conduit means for dissipating the heat absorbed by said gaseous medium from said liquid dielectric in passing through said tubes, said conduit means having a constriction therein between said manifold.

7. In combination, a casing, insulating liquid dielectric within said casing, a gaseous dielectric medium filling said casing above said liquid dielectric, a transformer core and coil assembly immersed in said liquid dielectric within said casing and including a magnetic core and electrical windings linking said core, a plurality of elongated, U- shaped, thin-walled, compliant tubes disposed adjacent the bottom and side walls of said casing, said tu'bes being spaced apart peripherally of the side walls of said casing and having open ends in communication with said gaseous medium, said tubes having high tensile strength and low modulus of elasticity and being in resonance with the vibratory forces originating in said core when said windings are energized, said tubes changing in volume at a frequency which is a function of said vibratory forces originating in said core and thereby effectively contributing compressibility to said liquid dielectric and reducing said vibratory forces tending to vibrate the walls of said casing, intake and exhaust manifolds each of which registers with one open end of said U-shaped tubes, conduit means communicating with both said manifolds and extending through the walls of said casing for inducing the circulation of said gaseous medium through said tubes and through said conduit means, and means for dissipating heat absorbed by said gaseous medium in circulating through said tubes.

8. In combination, a casing,

liquid dielectric within said casing,

a transformer core and coil assembly imblower and said intake mersed in said electrical windings linking said core, means for mechanically decoupling said core and coil assembly from said casing, means for reducing the vibratory forces originating in said core transmitted by said liquid dielectric tending to vibrate the walls of said casing including a plurality of elongated, thin-walled, spaced apart, compliant tubes of relatively high thermal conductivity immersed in said liquid dielectric between said core and coil assembly and the walls of said casing, a gaseous medium filling said tubes, said tubes being divided into a plurality of groups, intake and exhaust manifolds associated with each of said groups respectively in communication with the inlet and outlet ends of the tubes of said group, conduit means connecting the intake and exhaust manifolds of diiferent groups, said conduit means including at least one blower for inducing circulation of said gaseous medium in a path through said tubes and said manifolds and said conduit means, and means in said conduit mean-s for dissipating the heat absorbed by said gaseous medium from said liquid dielectric in circulating through said tubes.

9. In combination, a tank, an insulating liquid dielectric within said tank, a first gaseous insulating medium above said liquid within said tank, a transformer core and coil assembly immersed in said liquid dielectric within said tank including a magnetic core and electrical windings linking said core, means for mechanically decoupling said core and coil assembly from the walls of said tank, means for reducing the vibratory forces originating in said magnetic core transmitted by said dielectric liquid tending to vibrate the walls of said tank when said windings are energized including a plurality of elongated,

hollow, thin-walled spaced apart, U-shaped compliant tubes of high thermal conductivity immersed in said dielectric liquid adjacent the bottom and side walls of said tank and having the ends thereof extending above the surface of said liquid dielectric, intake and exhaust manifolds within said tank above said liquid dielectric each of which is in communication with and hermetically sealed to one open end of said U-shaped tubes, a second gaseous medium having high thermal conductivity within said tubes, means including conduit means registering with said intake and exhaust manifolds for inducing circulation of said second gaseous medium through said tubes, and means in said conduit means for dissipating the heat absorbed by said second gaseous medium in circulating through said tubes. 7

References Cited by the Examiner UNITED STATES PATENTS 1,846,887 2/ 1932 Mathews 336- 2,050,888 8/1936 Kirch 17412 X 2,711,882 6/1955 Narbut-ovskih 336--6l X 2,731,606 1/1956 Stewant et al 336l00 X 2,870,858 1/1959 Adams 336100 X FOREIGN PATENTS 931,294 5/1946 France.

LEWIS H. MYERS, Primary Examiner.

I. BURNS, Examiner.

W. M. ASBURY, T. J. KOZMA, Assistant Examiners. 

1. IN COMBINATION, A TANK, AN INSULATING DIELECTRIC LIQUID PARTIALLY FILLING SAID TANK, A GASEOUS DIELECTRIC MEDIUM FILLING SAID TANK ABOVE SAID LIQUID DIELECTRIC, A TRANSFORMER CORE AND COIL ASSEMBLY IMMERSED IN SAID LIQUID DIELECTRIC WITHIN SAID TANK AND INCLUDING A MAGNETIC CORE AND ELECTRICAL WINDINGS LINKING SAID CORE, MEANS FOR REDUCING THE VIBRATORY FORCES ORIGINATING IN SAID MAGNETIC CORE TRANSMITTED BY SAID DIELECTRIC LIQUID TENDING TO VIBRATE THE WALLS OF SAID TANK INCLUDING A PLURALITY OF ELONGATED, HOLLOW, THIN-WALLED SPACED APART, U-SHAPED, COMPLIANT TUBES OF HIGH THERMAL CONDUCTIVITY IMMERSED IN SAID DIELECTRIC LIQUID ADJACENT THE BOTTOM WALL AND SIDEWALLS OF SAID TANK AND HAVING OPEN ENDS IN COMMUNICATION WITH SAID GASEOUS MEDIUM, INTAKE AND EXHAUST MANIFOLDS EACH OF WHICH REGISTERS WITH ONE OPEN END OF SAID TUBES, MEANS INCLUDING CONDUIT MEANS COMMUNICATING WITH SAID MANIFOLDS FOR INDUCING CIRCULATION OF SAID GASEOUS MEDIUM THROUGH SAID TUBES, AND MEANS IN SAID CONDUIT MEANS FOR COOLING SAID GASEOUS MEDIUM AFTER IT HAS CIRCULATED THROUGH SAID TUBES. 